1. Field of the Invention
The present invention relates to a camera module including an imaging element having a rectangular light receiving surface and a lens for forming an image on the imaging element.
2. Description of the Related Art
Portable cameras and cameras built into mobile devices or the like typically include an imaging element (such as a CCD) and a lens for forming an image on the imaging element, and many of them are provided with an auto-focus mechanism for automatically adjusting the focus at the time of image capture and/or an anti-shake (or image stabilization) mechanism for reducing blur caused by camera shake due to hand-held shooting. To realize such mechanisms, there is proposed a camera module in which a lens (or lens holder) is supported by a spring member having a cantilever structure such that the lens is movable in a direction of the optical axis thereof and in a plane perpendicular to the optical axis, and the movement in each direction is controlled by magnetic driving (see JP 2011-65140A, for example).
The aforementioned camera module includes a lens barrel holding the lens coaxially, a lens holder receiving the lens barrel therein and holding the same, and a magnet holder coaxially surrounding the lens holder, wherein the lens holder is provided with a focusing coil and the magnet holder is provided with a permanent magnet to form an auto-focusing lens drive apparatus. The auto-focusing lens drive apparatus is supported by four suspension wires each having one end affixed to a base board having an imaging device mounted thereon, in such a manner that the entirety of the auto-focusing lens drive apparatus is rockable in two directions perpendicular to the optical axis. Further, the permanent magnet includes permanent magnet sections for camera-shake compensation, and camera-shake compensation coils are provided on coil boards disposed so as to face the permanent magnet sections, respectively, whereby a camera-shake correction apparatus is configured. In a portable device having a thus-configured camera module mounted thereon, it is possible to perform auto-focusing and camera-shake correction by controlling corresponding magnetic drive circuits.
However, in the camera module disclosed in JP 2011-65140A, the lens is circular in shape, and the lens barrel surrounding and holding the circular lens has a substantially cylindrical shape and is integrally fitted into the lens holder which has a substantially rectangular box-like shape. The focusing coil includes sections extending along four sides of the lens holder, and the permanent magnet sections are disposed on corresponding four sides of the magnet holder which surrounds the lens holder and has a substantially rectangular shape. Further, the camera-shake correction coils facing the relevant permanent magnet sections are disposed on the outside of the four sides of the magnet holder. Thus, four plate-shaped permanent magnet sections are respectively disposed on the four sides of a square having a center positioned on the optical axis of the lens (lens barrel) and the camera-shake correction coils are disposed on the outside of the permanent magnet sections, and this increases the size of the camera module particularly in the radial direction of the lens. Such a camera module will require a large space when installed into a portable device, thus making it difficult to reduce the size of the portable device.